Method of treating pellicles



4 in contact with Patented May- 4, 1937 UNITED srArss PATENT OFFICEMETHOD OF TREATING PELLICLES Thomas F. Banigan, Kenmore, N. Y.,assignor, by mesne assignments, to E. I. du Pont de Nemours & Company,Wilmington, Del., a corporation of Delaware No Drawing. Application"July 28, 1934,

Serial No. 737,428

iron stains, and in particular, it pertains to the treatment ofpellicles of non-fibrous character, such as those made from regeneratedcellulose,

. which are adapted for use as bottle caps, bands and the like, in orderto prevent staining of the pellicles when dried in contact with iron ormetals containing iron as a component.

Heretofore, when regenerated cellulose caps and bandsin a gel condition,i. e. after coagulation and regeneration but before being dried, wereapplied to bottles havingiron-containing metallic caps or appurtenances,a common defect has been that the cellulose caps and bands developedrust stains which appeared on the surface and greatly injured theappearance of the finished package. In addition, the portion stainedwith I rust became weakened and tended to crack at these points. l t

' Caps and bands of regenerated cellulose, which have been manufactured,for instance, by the viscose process, are customarily stored and shippedto consumers in an aqueous solution containing glycerin or othersoftener. The consumer withdraws thecap or band from the shippingsolution and applies it over the bottle or other desired container orobject and allows it to dry. Indrying, it shrinks considerably and gripsthe object tightly. If, in so doing, the cap orband comes intocontactwith iron or metal containing iron, rust stains will develop,which impart'an unsightly appearance and a destructhe action to the capor band. when the capor band is opaque, as for example when itcontains-titanium oxide or other pigment as an 0 opaquing agent, theunsightliness due to the ironstain is quitepronounced. It is an objectof this invention to produc non-fibrous pellicles which resist stainingwhen 'further object of this invention to prevent iron stains in capsand bands of non-fibrous sheet materials which are applied in a gelstate to hottles or other containers having iron-containing 5 metal capsor appurtenances, and which caps and bands attain their ultimatecondition as the result ofshrinkage through the loss of moisture. otherobjects-of the invention will appear hereinafter.

- The objects of this invention are accomplished,

50 in the preferred form, by shipping the covering material in anaqueous solution containing a small amount of a stain-preventativematerial of the type herein described.

I have discovered that iron stains can be greatly 55 diminished and evencompletely prevented by v f the bottles.

'. The alkalinity of these compounds is somewhat iron-containing metals.It is a I 8Claims., (Cl .21538) This invention relates to the preventionof ping container and the treating solution containing the desiredamount of glycerin and staininhibitor, then poured in until it coversthe pel- 15 licles, after which the container may be closed and shipped,and the treated caps, whenever desired, placed on the bottles or likevessels, and permitted to dry and shrink over the tops of Thosecompounds found tovbe effective in pre- 20 venting iron-staining ofpellicles of the character described herein are water-soluble compoundsyielding an alkaline reaction in aqueous solution.

less than that of a sodium hydroxide solution of equal concentration,and is not so great as to injure the cellulosic pellicle during storagein a shipping container or when in place on a bottle.

Preferred compounds of this character which operate to preventiron-staining of cellulosic-pellicles are tri-scdium phosphate (Na'sPCh)sodium pyrophosphate and triethanolamine. The scope of the inventionincludes the corresponding phosphates of the other alkali metals, e. g.potassium, and includes also other water-soluble salts which give asimilar alkaline reaction in water solution such as borates andsilicates of sodium and potasslum. The scope of the invention alsoincludes water-soluble amines other than triethanolamine. 40

. The compounds used in accordance with the present invention need onlyto be soluble in water to the extent desired to inhibit iron-staining,e. g. so as to form a concentration ordinarily not less than aboutone-half per cent. Compounds which would otherwise be suitable but whichhave a too high or a too low pH, when dissolved in aqueous solution, maysometimes be used by adding buffer materials so that the final pH may beregulated within the desired limits, for example, to obtain a final pHcorresponding to that of an aqueous solution of tri-sodium phosphate.

The 7 following illustrative examples describe modes of applying theinvention: i

. Example I.Gel caps and/or bands of regenerated cellulose prepared fromviscose and adapted to be applied to bottle tops and necks are packed ina shipping container containing glycerin and tri-sodium phosphate, insuch a concentration that, after equilibrium with the moisture in thecaps is reached, the shipping solution contains about 5% of glycerin andabout /g% of tri-sodium phosphate.

Example II.-The same procedure is followed as in Example I except thatthe solution, when equilibrium has been reached, contains one to threeper cent of sodium pyrophosphate. The caps and bands, when dried as inExample I, are almost completely free from rust stains after longperiods of usage.

Example III.-The same procedure is followed as in Example I, except thatthe equilibrium solution contains 0.2% triethanolamine.

Caps and bands treated in accordance with the preceding examples, whendried down over iron or iron-containing metal bottle caps, even when thelatter are filed down to expose the bare metal, remain completely freefrom rust stains even after a long period of time.

The proportion of anti-staining compounds present in the equilibriumsolution which is used to ship the pellicles may vary from a fraction ofa percent up to the limit of solubility of the compound in the solution.For most practical purposes, the equilibrium solution will contain fromone-tenth per cent to five per cent of said compound.

The invention, in its preferred form, applies to the treatment ofregenerated cellulose pellicles obtained from viscose, but it may alsobe applied to regenerated-cellulose pellicles obtained from cuprammoniumcellulose solution, or to the treatment of cellulose esters such ascellulose acetate, or to cellulose ethers such as ethyl cellulose orglycol celluose which have been cast in water solution, or to pelliclesof gelatin, casein and related substances. The invention may be appliedwherein any such pellicles come in contact with aware"? a shippingsolution which has attained equilibrium and shipped in a moist,condition to the point of use.

Any variation or modification which conforms to the spirit of theinvention is intended to be included within the'scope of the claims.

I claim:

1. The method which comprises treating nonfibrous cellulosic pellicleswhich are subject to shrinking by loss of water and which are subject tostaining when shrunk in contact with iron with an aqueous solution of asalt which reacts alkaline in water solution and which will inhibit theformation of an iron compound which wili discolor said pellicles.

2. The method which comprises treating nonfibrous cellulosic pellicleswhich are subject to shrinking by loss of water and which are subject tostaining when shrunk in contact with iron with an aqueous solution of analkali metal phosphate.

I 3. The method which comprises treating nonfibrous cellulosic pellicleswhich are subject to shrinking by loss of water and which are subject tostaining when shrunk in contact with iron with an aqueous solution ofsodium triphosphate.

4. The method which comprises treating nonfibrous cellulosic pellicleswhich are subject to shrinking by loss of water and which are subject tostaining when shrunk in contact with iron with an aqueous solution ofsodium pyrophosphate.

5. A cellulosic pellicle which is subject to shrinking by loss of waterand which is subject to staining when shrunk in contact with iron havingassociated therewith a colorless salt which reacts alkaline inwater andwhich will inhibit the formation of an iron compound which will discolorsaid pellicle.

6. A cellulosic pellicle which is subject to shrinking by loss of waterand which is subject to staining when shrunk in contact with iron havingassociated therewith alkali metal phosphate.

'I. A cellulosic pellicle which is subject to shrinking by loss of waterand which is subject to staining when shrunk in contact with iron havingassociated therewith sodium tri-phosphate.

8. A cellulosic pellicle which is subject to shrinking by loss of waterand which is subject to staining when shrunk' in contact with ironhaving associated therewith sodium pyro-phos- D a e.

THOMAS F. BANIGAN.

